Patent GB-1332185-A (GB)
Title: Document which is resistant to being reproduced
IPC: G03G21/04
Filed: 1970-10-06
Abstract: 1332185 Security paper XEROX CORP 6 Oct 1970 [7 Oct 1969] 47467/70 Heading B6A [Also in Division C4] A document resistant to being reproduced, comprises a support member bearing an image visible under ambient lighting conditions and in the form of marking material in informationdefining image areas, the marking material being confined to the image areas and the background being substantially free of the marking material and of material which can be converted thereto by exposure to actinic radiation, the document including a photochromic material, which may be the image material itself or a further material, distributed so that when the document is subjected to illumination above ambient light conditions such that the p./c. material colour changes, the document achieves a substantially uniform degree of darkness over at least a portion of the information containing area of the document, the portion containing both image and background areas. Erasure may be by heat radiating with light, such as visible or infra-red or applying hydrocarbon vapour such as toluene or benzene, for example. Several p./c. materials may be in vertical or horizontal strips checker board fashion or over all the surface. The photochromic compounds may be coatings adhering directly to the support member or may be in a transparent plastics. Bases may be Zn, Al, glass, brass, polyethylene, polypropylene, thermosetting resins (e.g. urea formaldehyde, and epoxies) and bond paper. A mixture of p./c. materials may be used to encompass the spectrum of various exposure sources. A mixture may be prepared by dissolving 6<SP>1</SP>-nitro-1,3,3-trimethylindolinobenzospiropyran in a solvent such as toluene or benze and a binder such as polystyrene or methylmethacrylate, the solution used to coat or impregnate paper. When colour change is too slow to prevent a first copy, modified copiers may be used. An extra light source is provided as it travels to the exposure station, or may be exposed to a regular light source prior to a shutter release. Also a special copier may furnish copies of an original on non- reproducable photochromic treated paper, the copier employing p./c. toner imaging marking material, and a p,/c. treated recording sheet. Use of documents in which the marking material is p./c. and reverts to the same colour as the paper inhibits copying. Examples of p./c. spiropyrans are disclosed and inorganic materials, e.g. glasses, doped alkaline earth sulphides, (e.g. calcium, magnesium and barium sulphide: Mn); copper halides (e.g. cuprous chloride); mercuric halides, mercuric cyanates, thiocyanates and selenides; the selenocyanides (e.g. chloro-mercuric selenocyanide, bromomercuric selenocyanide, hydrosulpho-mercuric selenocyanide, hydroseleno-mercuric selenocyanide) ; hydroseleno-mercuric sulphocyanide, activated titanium dioxide, bismuth oxalate, lithium amide, and mixtures thereof and as described in U.S. Patent Specification 3,422,759. Examples of p./c. spiropyrans are disclosed. Business forms, maps, film transparencies, drawings, schematics, military order and plans are exemplified.